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Search Results: 1 - 10 of 33516 matches for " Peter Johansson "
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Insomnia is associated to depressive symptoms in patients with chronic heart failure  [PDF]
Peter Johansson, Anders Brostr?m
Open Journal of Nursing (OJN) , 2013, DOI: 10.4236/ojn.2013.31005
Introduction: Insomnia and depressive symptoms are common among patients with chronic heart failure (HF). Aim: The aim was to describe the prevalence of insomnia and depressive symptoms, as well as to examine the association between insomnia and depressive symptoms in patients with HF. Method: A crosssectional descriptive study including 212 patients with HF. All patients responded to questionnaires regarding sleeping difficulties (Uppsala Sleep Inventory-Chronic Heart Failure), daytime sleepiness (Epworth Sleepiness Scale) and depressive symptoms (The Mental Health Scale). Results: Patients with depressive symptoms (34%) had, compared to those without, significantly more major complaints of insomnia as indicated by the sub-types; non-restorative sleep (66% vs. 32%, p < 0.0001), difficulty in maintaining sleep (35% vs. 16%, p = 0.003), difficulty in initiating sleep (29% vs. 14%, p = 0.009) and early morning awakenings (25% vs. 10%, p = 0.004). The odds ratio (OR) to suffer from depressive symptoms; were for; non-restorative sleep 5.2 (CI 95%, 2.2 - 12.3), difficulties maintaining sleep 2.5 (CI 95%, 1.2 - 4.9), difficulties in initiating sleep 2.2 (CI 95%, 1.1 - 4.4) and early morning awakenings 2.4 (CI 95%, 1.1 - 5.4). When categorising insomnia into three severity groups, 1) non insomnia, 2) mild insomnia, and 3) severe insomnia, the OR for depressive symptoms for the mild insomnia and severe insomnia group were 2.2 (CI 95%, 1.1 - 4.2) and 7.4 (CI 95%, 2.4 - 22.8) respectively, compared to the non insomnia group. Conclusion: Insomnia is independently associated to depressive symptoms. Assessment of depressive symptoms and insomnia in patients with HF is important since treatment could be targeted to depressive symptoms only and/or to the sleep disturbance.
Eskers and bedrock gorges (tunnel valleys) in the Pakasaivo area, western Finnish Lapland
Peter Johansson
Bulletin of the Geological Society of Finland , 2003,
Abstract: Studies of the deglaciation of the last Scandinavian Ice Sheet, including the behavior of the ice sheet and meltwater activity, were conducted in the vicinity of the Pakasaivo canyon lake, located in western Finnish Lapland. Pakasaivo itself, a circular basin up to 100 m deep, was formed in the broken bedrock by glacial erosion and meltwater streams. It was originally related to a former subglacial meltwater system, including the deep Keinokursu gorge. Both this gorge and the Pakasaivo canyon lake were formed subglacially duringan early stage of deglaciation. It was characterized by intense meltwater erosion, which in Pakasaivo also seems to have generated a strong whirl. Steep-crested esker ridges were subsequently deposited; subaerial meltwater activity then followed. Finally the meltwaterwas discharged from the ice-dammed lake north of the area and passed through the Pakasaivo canyon to the ice-free areas. This caused additional intense erosion of the canyon floor and walls, and the deep circular basin is highly similar to a plunge pool formed at the base of a cataract.
Cyclotron resonance lineshape in a Wigner crystal
Peter Johansson
Physics , 1994, DOI: 10.1103/PhysRevB.50.14734
Abstract: The cyclotron resonance absorption spectrum in a Wigner crystal is calculated. Effects of spin-splitting are modelled by substitutional disorder, and calculated in the coherent potential approximation. Due to the increasing strength of the dipole-dipole interaction, the results show a crossover from a double-peak spectrum at small filling factors to a single-peak spectrum at filling factors $\agt 1/6$. Radiation damping and magnetophonon scattering can also influence the cyclotron resonance. The results are in very good agreement with experiments.
Light scattering from disordered overlayers of metallic nanoparticles
Peter Johansson
Physics , 2001, DOI: 10.1103/PhysRevB.64.165405
Abstract: We develop a theory for light scattering from a disordered layer of metal nanoparticles resting on a sample. Averaging over different disorder realizations is done by a coherent potential approximation. The calculational scheme takes into account effects of retardation, multipole excitations, and interactions with the sample. We apply the theory to a system similar to the one studied experimentally by Stuart and Hall [Phys. Rev. Lett. {\bf 80}, 5663 (1998)] who used a layered Si/SiO$_2$/Si sample. The calculated results agree rather well with the experimental ones. In particular we find conspicuous maxima in the scattering intensity at long wavelengths (much longer than those corresponding to plasmon resonances in the particles). We show that these maxima have their origin in interference phenomena in the layered sample.
Light emission from a scanning tunneling microscope: Fully retarded calculation
Peter Johansson
Physics , 1998, DOI: 10.1103/PhysRevB.58.10823
Abstract: The light emission rate from a scanning tunneling microscope (STM) scanning a noble metal surface is calculated taking retardation effects into account. As in our previous, non-retarded theory [Johansson, Monreal, and Apell, Phys. Rev. B 42, 9210 (1990)], the STM tip is modeled by a sphere, and the dielectric properties of tip and sample are described by experimentally measured dielectric functions. The calculations are based on exact diffraction theory through the vector equivalent of the Kirchoff integral. The present results are qualitatively similar to those of the non-retarded calculations. The light emission spectra have pronounced resonance peaks due to the formation of a tip-induced plasmon mode localized to the cavity between the tip and the sample. At a quantitative level, the effects of retardation are rather small as long as the sample material is Au or Cu, and the tip consists of W or Ir. However, for Ag samples, in which the resistive losses are smaller, the inclusion of retardation effects in the calculation leads to larger changes: the resonance energy decreases by 0.2-0.3 eV, and the resonance broadens. These changes improve the agreement with experiment. For a Ag sample and an Ir tip, the quantum efficiency is $\approx$ 10$^{-4}$ emitted photons in the visible frequency range per tunneling electron. A study of the energy dissipation into the tip and sample shows that in total about 1 % of the electrons undergo inelastic processes while tunneling.
Electromagnetic Green's function for layered systems: Applications to nanohole interactions in thin metal films
Peter Johansson
Physics , 2010, DOI: 10.1103/PhysRevB.83.195408
Abstract: We derive expressions for the electromagnetic Green's function for a layered system using a transfer matrix technique. The expressions we arrive at makes it possible to study symmetry properties of the Green's function, such as reciprocity symmetry, and the long-range properties of the Green's function which involves plasmon waves as well as boundary waves, also known as Norton waves. We apply the method by calculating the light scattering cross section off a chain of nanoholes in a thin Au film. The results highlight the importance of nanohole interactions mediated by surface plasmon propagating along the chain of holes.
The role of cold and hot gas flows in feeding early-type galaxy formation
Peter H. Johansson
Physics , 2014,
Abstract: We study the evolution of the gaseous components in massive simulated galaxies and show that their early formation is fuelled by cold, low entropy gas streams. At lower redshifts of z<3 the simulated galaxies are massive enough to support stable virial shocks resulting in a transition from cold to hot gas accretion. The gas accretion history of early-type galaxies is directly linked to the formation of their stellar component in the two phased formation scenario, in which the central parts of the galaxy assemble rapidly through in situ star formation and the later assembly is dominated primarily by minor stellar mergers.
Breather mobility and the PN potential: Brief review and recent progress
Magnus Johansson,Peter Jason
Physics , 2014, DOI: 10.1007/978-3-319-21045-2_6
Abstract: The question whether a nonlinear localized mode (discrete soliton/breather) can be mobile in a lattice has a standard interpretation in terms of the Peierls-Nabarro (PN) potential barrier. For the most commonly studied cases, the PN barrier for strongly localized solutions becomes large, rendering these essentially immobile. Several ways to improve the mobility by reducing the PN-barrier have been proposed during the last decade, and the first part gives a brief review of such scenarios in 1D and 2D. We then proceed to discuss two recently discovered novel mobility scenarios. The first example is the 2D Kagome lattice, where the existence of a highly degenerate, flat linear band allows for a very small PN-barrier and mobility of highly localized modes in a small-power regime. The second example is a 1D waveguide array in an active medium with intrinsic (saturable) gain and damping, where exponentially localized, travelling discrete dissipative solitons may exist as stable attractors. Finally, using the framework of an extended Bose-Hubbard model, we show that while quantum fluctuations destroy the mobility of slowly moving, strongly localized classical modes, coherent mobility of rapidly moving states survives even in a strongly quantum regime.
Butterfly-like spectra and collective modes of antidot superlattices in magnetic fields
Egidijus Anisimovas,Peter Johansson
Physics , 1999, DOI: 10.1103/PhysRevB.60.7744
Abstract: We calculate the energy band structure for electrons in an external periodic potential combined with a perpendicular magnetic field. Electron-electron interactions are included within a Hartree approximation. The calculated energy spectra display a considerable degree of self-similarity, just as the ``Hofstadter butterfly.'' However, screening affects the butterfly, most importantly the bandwidths oscillate with magnetic field in a characteristic way. We also investigate the dynamic response of the electron system in the far-infrared (FIR) regime. Some of the peaks in the FIR absorption spectra can be interpreted mainly in semiclassical terms, while others originate from inter(sub)band transitions.
Assembly Histories and Observational Properties of Simulated Early-type Galaxies
Peter H. Johansson
Physics , 2012, DOI: 10.1017/S1743921313005358
Abstract: We demonstrate that massive simulated galaxies assemble in two phases, with the initial growth dominated by compact in situ star formation, whereas the late growth is dominated by accretion of old stars formed in subunits outside the main galaxy. We also show that 1) gravitational feedback strongly suppresses late star formation in massive galaxies contributing to the observed galaxy colour bimodality that 2) the observed galaxy downsizing can be explained naturally in the two-phased model and finally that 3) the details of the assembly histories of massive galaxies are directly connected to their observed kinematic properties.
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